Check for the "propertyNotFound" exception in addition to the warning
Check for the "propertyNotFound" exception in addition to the warning

This makes this test fit equivalent tests checking for warning and exception.
Also, this is a preparation for a following commit to be able to add a test that
checks for *no* exception emitted.

AbletonAG/aqt-stylesheets,AbletonAG/aqt-stylesheets